Epithelial-Mesenchymal Transition Drives Three-Dimensional Morphogenesis in Mammalian Early Development

Abstract

From fertilization to onset of gastrulation, a mammalian embryo goes through several rounds of cellular morphogenesis resembling phenomena of epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET), collectively referred to as EMTs. How these EMT events play a role in shaping the three-dimensional (3-D) architecture of the developing embryo is not well-understood. In this review, we present a model in which cellular morphogenesis, represented primarily by dynamic changes in its epithelialization status, is the driving force of embryonic 3-D organization. This is achieved through the integration of three key components of mammalian early development, the pluripotency regulation, morphogenetic signaling, and biomechanical force anisotropy. Although cells in an early embryo do not exhibit full mesenchymal characteristics, our model underscores the importance of investigating molecular regulation of epithelial cell polarity and partial EMT/MET in understanding mammalian early development.

Epithelial and Neural Cadherin in Mammalian Fertilization: Studies in the Mouse Model

“…The molecular events involved in EMT are highly complex, and comprise a decrease in expression of epithelial markers, such as E-cad, accompanied by an increase in the expression of mesenchymal markers, such as N-cad, changes that provide cell plasticity and result in increased cell migration and invasion properties. EMT-related events have been fully characterized in early embryogenesis [ 87 , 88 ]. An EMT-like process may, at least in part, be responsible for the progression from adhesion to fusion in gamete interaction, considering the striking similarities to these mechanisms already identified in gametes.…”